Dewaxing of lubricating oils

ABSTRACT

LUBRICATING OIL DISTILLATES CONTAINING BOTH PARAFFIN WAX AND MICROYCRYSTALLINE EAX, ARE DEWAXED IN A PROCESS COMBINING CATALYTIC HYDRODEWAXING AND CENTRIFUGE DEWAXING.

United States Patent 3,654,128 Patented Apr. 4, 1972 3,654,128 DEWAXING F LUBRICATING OILS Robert A. Woodie, Nederland, Tex., assignor to Texaco Inc., New York, N.Y. No Drawing. Filed Dec. 24, 1969, Ser. No. 888,050 Int. Cl. Cg 43/08 US. Cl. 20833 4 Claims ABSTRACT OF THE DISCLOSURE Lubricating oil distillates containing both paraffin wax and microcrystalline wax, are dewaxed in a process combining catalytic hydrodewaxing and centrifuge dewaxing.

BACKGROUND OF THE INVENTION This invention relates to a process of producing lubricating oils from waxy distillates. More specifically, it relates to producing lube oils from distillates containing both parafiin wax and microcrystalline wax. The invention is particularly related to a sequence of operations for the selected elimination of waxy materials from lubrieating oil base stocks.

During the last 25 to 30 years, sweating and pressing operations of waxy lubricating oil base stocks have rapidly been replaced by solvent dewaxing processes. The waxy distillate is mixed with a solvent which is a good solvent for oil but a poor one for wax. The mixture is then chilled to form wax crystals which are removed from the solvent-oil mixture by use of a large rotary filter. The solvent-oil mixture is subsequently separated by distillation and the Wax is recovered for further processing. Solvents are usually mixtures and include such combinations as methyl ethyl lcetone-toluene, benzene-toluene, liquid sulfur dioxide-benzene and ethylene dichloridebenzene. Waxy distillates containing both parafiin waxes and microcrystalline waxes present processing problems with solvent dewaxing since the microcrystalline wax has such small particles that it plugs the openings in the filter cloths of the rotary filters in a solvent dewaxing plant.

One method employed heretofore has been to split the waxy distillate into a low boiling waxy distillate, i.e., boiling below about 845-860 R, which contains predominantly paraffin wax and a higher boiling cylinder stock, boiling above about 845-860 R, which contains the microcrystalline wax. The lower-boiling cut is subjected to solvent dewaxing to remove the paraffin wax and is then distilled to separate the dewaxed oil into solvent neutral oils of various viscosities.

The microcrystalline wax in the cylinder stock is removed conventionally in a centrifuge process. The cylinder stock is diluted with naphtha, chilled and introduced into a high speed centrifuge which throws the heavy wax rich solution to the outer edge of the centrifuge and the lighter naphtha and oil solution to the center where it is removed. The wax solution rises to the sides of the centrifuge where it is contacted with a stream of hot water to prevent solidification and is removed. After separation of the naphtha from the wax-free oil, the high viscosity oil is fractionated to produce blending oils, known as bright stocks, which when combined with the solvent neutral oils produced by solvent dewaxing produce the numerous grades of lubricating oils necessary to fill customer demands.

When processing a waxy distillate containing both parafiin wax and microcrystalline wax it should be highly desirable to employ a processing sequence which would eliminate the present requirement of separating the distillate into two feedstocks, one containing the paraffin wax and the other containing the microcrystalline wax followed by blocked-out operations and subsequent combining of the dewaxed stocks to produce lubricating oils.

SUMMARY OF THE INVENTION I have found that significant improvements can be realized in the lubricating oil processing sequence whereby a waxy distillate containing both parafiin wax and microcrystalline wax can be processed in a sequence of steps which will produce a lubricating oil distillate substantially free of both types of waxes without the necessity of separation of the distillate into two feedstocks with separate blocked-out processing of each feedstock. Broadly, my invention is directed to a combination process where the lubricating oil stock is subjected to a particular sequence of steps involving catalytic dewaxing which selectively removes the paraflin wax and centrifuge dewaxing which removes the microcrystalline wax.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Broadly I have found that significant improvements in the preparation of lubricating oils from base stocks containing both paratfin wax and microcrystalline wax can be realized by subjecting the lubricating oil base stocks to a sequence of steps involving catalytic dewaxing and centrifuge dewaxing. This processing is accomplished without the necessity of separating the waxy distillate into a low boiling fraction and a high boiling fraction as was required heretofore. By operating in this fashion it is possible to obtain lubricating oil base stocks having low pour point qualities which may be used to prepare a wide variety of lubricating oils.

My invention contemplates a process for the production of lubricating oil which comprises:

(a) Contacting a waxy distillate comprising paraflin wax and microcrystalline wax with a catalyst comprising a hydrogenating component on a hydrogen mordenite under paraffin dewaxing conditions, and

(b) Then, subjecting the parafiin-dewaxed distillate to centrifuge dewaxing.

More particularly this process comprises:

(a) Contacting a hydrocarbon oil comprising parafiin wax and microcrystalline wax in a reaction zone at a temperature in the range of 450-950 F. with a hydrogen mordenite and having associated with said mordenite a Group V-IH metal.

(b) Recovering from said reaction zone a first eflluent comprising said hydrocarbon oil having a substantially reduced paraflin wax content,

(c) Admixing naphtha with said first efiluent producing a second eflluent,

(d) Cooling said second eflluent to between 0 and --40 F.,

(e) Subjecting said second efiluent to centrifuge dewaxing and (f) Recovering a third effluent comprising said hydrocarbon oil having a substantially reduced parafiin Wax and microcrystalline wax content.

In the catalytic dewaxing operation, the waxy distillate undergoing treatment is contacted with a crystalline aluminosilicate in decationized form and containing a hydrogenating component. The aluminosilicate used, mordenite, selectively cracks the paraffin waxes to lighter materials which are subsequently removed. The mordenite employed may be either the natural or synthetic variety but regardless of the type used the mordenite must be decationized, i.e., it must be in the hydrogen form in order to be effectively employed, Although normally available in sodium form, mordenite may be converted to the hydrogen form by contacting with a dilute acid such as hydrochloric acid or by exchanging the sodium with ammonium ions followed by heating or calcining to drive off ammonia. Both sodium mordenite and decationized or hydrogen mordenite have a mole ratio of silica to alumina of about 10 to l. A form of hydrogen mordenite which is especially preferred in the process of my invention is one wherein the silica to alumina ratio has been increased above 10 to l, particularly between 20 to 1 and 60 to 1. An extremely effective means of increasing the silica to alumina ratio is by acid leach ing, although care must be exercised not to destroy the crystal integrity of the mordenite by too severe leaching.

Acid treating and exchanging with ammonia to produce decationized aluminosilicates are techniques well known in the art of catalyst manufacture.

Other crystalline aluminosilicates such as zeolite A, faujasite, zeolite X or zeolite Y are unsuitable in the catalytic dewaxing process; only decationized mordenite is satisfactory for the purpose of the present invention.

The hydrogenating component which is incorporated with the mordenite comprises a Group VIII metal of compound thereof, for example, an oxide or sulfide which in addition may be associated with a Group VI metal or compound thereof. Noble metals such as platinum, palladium and rhodium have been found especially useful and may be used in amounts of 0.1-% based on the total catalyst weight with a range of 0.52.5% being preferred. Other suitable hydrogenating components comprise nickel, cobalt and iron, particularly when used in conjunction with a Group VI metal such as molybdenum or tungsten. Suitable combinations include cobaltmolybdenum, nickel-molybdenum and nickel-tungsten. This latter type of hydrogenating component may be present in an amount ranging from 540% by weight, preferably 25 The hydrogenating component may be incorporated into the support by ion exchange or by impregnation each of which is well known in the art.

i[n the catalytic dewaxing stage of the process the waxy components are selectively cracked to lighter components having a boiling point considerably lower than the desired lubricating oil fraction and therefore are easily separated therefrom, The principal by-products of the catalytic dewaxing process are light hydrocarbons such as ethane, propane and butane. Although the catalytic dewaxing step removes paraffin waxes as does a solvent dewaxing operation, the presence of microcrystalline wax does not interfere with the catalytic dewaxing operation as they do with solvent dewaxing wherein the microcrystalline waxes plug the openings in the filter cloths. Preferred operating conditions for catalytic dewaxing include: space velocity in the range of 0.1 to 10 volumes of feed/volume of catalyst/hr., preferably 0.25 to 5 LHSV; temperature in the range of about 450-950 F., preferably 500-850 F. and pressure within the range of atmospheric to 5000 p.s.i.g., preferably in the range of 200-1500 p.s.i.g.

Hydrogen, though not necessary for the selective catalytic activity of the mordenite, is advantageously employed to extend the life of the catalyst. Hydrogen may be used in amounts up to 20,000 standard cubic feet per barrel of charge with rates of 50010,000 s.c.f.b. being preferred. The hydrogen need not be pure and gases containing more than 65 volume percent hydrogen may be used. Reformer by-product hydrogen, hydrogen produced by the partial oxidation of hydrocarbon materials followed by shift conversion and electrolytic hydrogen are satisfactory.

Catalytic dewaxing of waxy distillates with hydrogen mordenite containing a hydrogenating component as discussed above is proposed in copending application Ser. No. 558,569, filed June 20, 1966, now Pat. No. 3,539,498 while catalytic dewaxing of mordenite having silica: alumina ratios above about 10 to 1 is proposed in c0- pending application Ser. No. 692,818, filed Dec. 22, 1967.

The oil recovered from the catalytic dewaxing step is substantially free of paratfin wax but contains essential- 1y all of the microcrystalline wax initially present in the waxy distillate, This partially dewaxed stream is then subjected to centrifuge dewaxing for the removal of the microcrystalline wax. This process is well known to those skilled in the art and has been employed in the petroleum processing industry for a number of years. Initially the waxy distillate is combined with a light hydrogen solvent, such as light straight run gasoline to produce a mixture containing about 60 to percent solvent. This mixture is chilled to a temperature of from 0 to 40 F. below the desired final pour point of the dewaxed oil, which in most instances would be between 0 and 40 F, and then introduced into a high speed centrifuge. The centrifugal force operates the microcrystalline wax from the mixture of oil and solvent with the wax being forced to the outer edge of the centrifuge and the light naphtha oil solution passing from the centrifuge through a tube located at the center thereof. The waxy material rises up the sides of the centrifuge bowl to its outlet where it is contacted with a stream of warm water to prevent solidification on the walls of the centrifuge and at the outlet. The mixture of microcrystalline wax and water is then separated in a heated tank. The hydrocarbon solvent is recovered from the mixture of lubricating oil and solvent by fractionation for reuse in the process. The recovered lubricating oil may be further fractionated to produce a number of dewaxed lubricating oil blending stocks which are subsequently reblended in varying amounts to produce the desired lubricating oil blends of proper viscosity and color.

The following examples illustrate the process of this invention.

EXAMPLE I A furfural refined waxy distillate having an API gravity of 29.0, a COC flash point of 515 F., a paraffin wax content of 7.1% and a microcrystalline wax content of 2.8% was heated and passed through a reaction vessel containing a fixed bed of decationized mordenite having a silica to alumina ratio of about 10 to 1 and having deposited thereon 1 wt. percent palladium. The operating conditions in the reactor included at pressure of 850 p.s.i.g., a temperature of 775 F. and a space velocity of 0.49 LHSV. Hydrogen was present in the reactor in an amount of 9200 s.c.f.b. The catalytically processed oil was then combined with 2 parts of naphtha, chilled to 35 F. and centrifuged. The recovered oil-naphtha mixture was stripped to produce the final dewaxed oil. The properties of the feed, intermediate and final product are presented in Table I below.

In a maner similar to that of Example I a refined turbine oil distillate having an API gravity of 28.7", a COC flash point of 480 F a paraffin wax content of 7.6% and a microcrystalline wax content of 3.3% was catalytically dewaxed over 1% palladium deposited on decationized mordenite having a silica to alumina ratio of about 10 to l at a temperature of 700 F., pressure of 850 p.s.i.g., a space velocity of 0.50 LHSV and a hydrogen rate of 8600 s.c.f.b. The partially dewaxed oil was then centrifuged dewaxed after being mixed with three parts of naphtha and chilled to -l0 F. The properties of the charge, intermediate and final products are presented in Table II below.

In a companion set of runs, centrifuge dewaxing of the waxy distillates of Examples I and II was attempted without being previously subjected to catalytic dewaxing. In neither case would the wax flow from the centrifuge.

I claim:

1. A process of removing crystalline and microcrystalline waxes from a hydrocarbon oil which comprises:

(a) contacting a hydrocarbon oil comprising paraffin wax and microcrystalline wax in a reaction zone at a temperature in the range of 450-950 F. with a hydrogen mordenite and having associated with said mordenite a Group VIII metal,

(b) recovering from said reaction zone a first hydrocarbon efliuent comprising said hydrocarbon oil having a substantially reduced paraffin wax content and a substantially unreduced microcrystalline wax content,

(c) admixing naphtha with said first efliuent producing a second effiuent,

(d) cooling said second effluent to between 0 and (e) subjecting said second effluent to centrifuge dewaxing, and

(f) recovering a third efiluent comprising said hydrocarbon oil having a substantially reduced paraflin wax and microcrystalline wax content.

2. A process according to claim 1 wherein step (a) is conducted in the presence of hydrogen.

3. A process according to claim 1 wherein the Group VIII metal comprises 0.1-5 of the total catalyst weight and is selected from the group consisting of platinum, palladium and rhodium.

4. A process according to claim 1 wherein a Group VI metal is associated with the Group VIII metal, the Group VIII metal is selected from the group consisting of nickel, cobalt and iron and the combined metals comprise 5-40% of the total catalyst weight.

References Cited UNITED STATES PATENTS 1,927,057 9/1933 Anderson 208-33 1,956,780 5/1934 Voorhees 20833 3,438,887 4/1969 Morris et a1. 20828 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 208-28 

